This invention relates to a mobile radio communication system and to a method of registering position in this system. More particularly, the invention relates to a mobile radio communication system, as well as to a position registration method thereof, in which a position registration area number is reported from a base station to a mobile station within a radio zone, position information indicating a position registration area in which a mobile station resides is stored based upon position registration information that has been transmitted from the mobile station, and when there is an incoming call to a mobile station, a paging call is placed from a plurality of base stations within the position registration area, in which the base station resides, based upon the position information.
In a mobile radio communication system, a base station notifies all mobile stations within a cell of common information such as a position registration area number, a mobile station refers to this reported information, performs monitoring to determine whether it has moved into a position registration area different from that until now and, if it moves into such an area, transmits a position registration signal to a mobile communication control station, which has a radio channel control function or a mobile communication control function, via a base station. The mobile communication control station, under the control of a position registration controller, registers subscriber data of the mobile station and position information indicating the position registration area in which the mobile station resides in a database of a home memory station based upon the position registration signal. When there is an incoming call to the mobile station, a gateway exchange obtains a mobile communication control station, which conforms to the position registration area in which the call-terminating mobile station resides, by referring to the position information that has been stored in the database, and places a paging call from a plurality of base stations within the position registration area in which the mobile station resides via the mobile communication control station.
FIG. 35 is a diagram showing the configuration of a mobile radio system. Mobile stations MS1 to MS8 are terminals capable of bi-directional radio communication with base stations BS1 to BS8. The base stations BS1 to BS8 are capable of radio communication with the mobile stations MS1 to MS8 within radio zones C1 to C8 that are centered on respective ones of the base stations BS1 to BS8. The radio zones C1 and C2 of base stations BS1 and BS2 construct a position registration area (or paging call area) PRA1, the radio zones C3 and C4 of base stations BS3 and BS4 construct a position registration area PRA2, the radio zones C5 and C6 of base stations BS5 and BS6 construct a position registration area PRA3, and the radio zones C7 and C8 of base stations BS7 and BS8 construct a position registration area PRA4.
Mobile communication control stations MSC1 and MSC2 have functions for implementing call connection control and service control, etc., for the purpose of providing mobile communication services. Of these stations, the mobile communication control station MSC, is connected to base station BS1 to BS4 and the mobile communication control station MSC2 is connected to base station BS5 to BS8. A gateway mobile communication exchange GS is an exchange that receives calls from another network to contract subscribers in its own network or to roaming subscribers in its own network. The mobile communication control stations MSC1 and MSC2 within this exchange's own network are connected via a communication line. Further, the gateway mobile communication exchange GS is connected to a database HLR of a home memory station HMS via a control signal line so as to be capable of referring to position information.
The database HLR is a database that stores subscriber data of the mobile stations MS1 to MS4 that reside in the position registration areas PRA1 to PRA4 and position information indicating in which of the areas the mobile stations reside. The mobile communication control stations MSC1, MSC2 receive position registration signals from the mobile station BS1 to BS8, thereby updating the stored content of the database HLR and registering information therein.
When the mobile station MS1 receives an incoming call, a paging call is placed from all of the base stations BS1, BS2 within the position registration area PRA1, in which the call terminating mobile station resides, by referring to the database HLR.
FIG. 36 is a diagram useful in describing an overview of a position registration and call terminating procedure in mobile radio communication.
The base stations BS1, BS2 report information for position registration to the mobile stations MS1, MS2 by notification information. If the mobile station MS2 residing in the position registration area PRA1 (see FIG. 35) moves into position registration area PRA2 under these conditions, as indicated by the dashed line, the mobile station MS2 detects the change in position registration area by way of the notification information from the base station BS3. As a result, the mobile station MS2 transmits a position registration signal. This position registration signal is sent to the mobile communication control station MSC1 via the base station BS3. The mobile communication control station MSC1 executes an authentication procedure if it receives a position registration signal. If the result of authentication is normal, the communication control station instructs the database HLR to perform position registration, thereby registering a routing number to this control station as well as position information, and sends a position-registration receipt number back to the mobile station MS2. Upon being instructed by the mobile communication control station MSC1 to perform position registration, the database HLR registers the routing number and position information that indicates the position registration area in which the mobile station MS2 resides. Registration of position at such time that the mobile station moves into another position registration area is completed by the above operation.
If the mobile station MS2 receives an incoming call, the gateway mobile communication exchange GS extracts the subscriber number (mobile station number) of the mobile station MS2 from the received dial number, reads position information (the routing number) of the mobile station MS2 from the database HLR based upon the subscriber number and sets up a path to the mobile communication control station MSC1 indicated by this routing number. As a result, the mobile communication control station MSC1 instructs all base stations BS3, BS4 within the position registration area PRA2 to perform a paging call. In response to the paging call, the mobile station MS2 transmits an answer signal to the mobile communication control station MSC1 via the base station. In response to the answer signal, the mobile communication control station MSC1 establishes an available communication channel TCH through a well-known procedure and sets up a connection.
Thus, regardless of where a mobile station moves, position information indicative of the position registration area in which the mobile station resides is updated and registered in the database HLR of the home memory station HMS, as a result of which the mobile station is capable of receiving an incoming call from a calling party in another network.
FIG. 37 is an explanatory view illustrating the relationship between the size of a position registration area and amount of control information. If a position registration area is increased in size, the number of resident mobile stations at the time of a paging call. As a consequence, there is an increase in the number of call channels in order to distinguish among the mobile stations and there is an increase in amount of control information. If a position registration area is decreased in size, on the other hand, it is necessary to notify of a change in position registration frequently. When a position registration area is small, therefore, the amount of control information of position registration increases. There have been various proposals for setting the size of position registration areas so as to optimize the efficiency of paging call traffic and position registration traffic.
FIG. 38 is an explanatory view (see Japanese Patent No. 2987780) illustrating position registration areas of a mobile telephone system already proposed. Here C1 to C8 represent radio zones, and L1-1 to L1-4 denote position registration areas of a position registration area pattern of a first system, L2-1, L2-4 position registration areas of a position registration area pattern of a second system and L3-1 a position registration area pattern of a third system. According to this prior art, position registration area patterns of a plurality of systems of different sizes (ranges of movement) are prepared and an optimum position registration area pattern is assigned to each mobile station in accordance with the area of the range of motion, i.e., in accordance with the position registration traffic of each mobile station.
Another example of the prior art (see the specification of Japanese Patent Application Laid-Open No. 4-249925) is a position registration system that records, at both a mobile communication control station and mobile station, past radio zones for which positions have been registered as well as the particular times. In accordance with the recorded data, the mobile communication control station updates position registration automatically even if no position registration signal from the mobile station arrives. If the mobile station, on the other hand, is at a position the same as a predicted position that is based on the recorded data, the mobile station does not issue a position registration signal. If it is at a different position, then the mobile station issues a position registration signal. For example, this system is such that if, because of the user commuting to work, a mobile station (1) is present in radio zone C1 every morning at 8:00 AM and (2) is present in radio zone C2 at around 8:30 AM, this information is stored by the mobile communication control station and mobile station, whereby position registration need not be carried out if the mobile station moves in accordance with such a routine.
Though the first example of the prior at makes it possible to reduce the traffic involved in position registration, the reduction in traffic is inadequate because it is still necessary to update (to perform position registration of) the position registration area whenever a mobile station moves into a different position registration area. In addition, position registration is required even in a case where a mobile station moves with a certain regularity.
Though the second example of the prior art does not in principle require position registration, it is applicable only to a mobile station that exhibits customary behavior and, hence, the range of application is limited.